JPH0283556A - Color image forming device - Google Patents

Abstract

PURPOSE:To prevent the filming of color toner effectively and to improve image reliability by providing a means which develops a photosensitive body only by a black developing device except in color image forming and a means which cleans the photosensitive body not through a transfer process after the development only by the black developing device. CONSTITUTION:This device has the means which develops the photosensitive body only by the black developing device 7 except in color image formation and the means 140 which cleans the photosensitive body not through the transfer process after the development only by the black developing device 7. Then the development only by the black developing device 7 is carried out at a proper period except in the color image formation and a developed image is cleaned by a cleaning device not through the transfer process to remove sticking matter such as filming formed of color other other hand a black developer together. Consequently, the filming of the color toner is prevented effectively to improve the image reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image forming apparatus, such as a color copying machine or a color printer, which has a color developer in addition to a black developer.

[Prior Art] According to a color image forming apparatus, a latent image to be developed in a predetermined color is formed on a photoreceptor by an optical system, and the latent image is developed in the predetermined color by a developing device. The developed image is transferred to a transfer material on a transfer drum, an intermediate transfer belt, or the like. Thereafter, a latent image to be developed in a predetermined color is formed on the photoreceptor by an optical system, and this latent image is developed by a developing device that performs development in the next color, and the resulting developed image is transferred to a transfer drum. The image is transferred onto an upper transfer material or an intermediate transfer belt, overlapping the previous transfer image. In this way, predetermined colors are developed and transferred one after another. After each transfer, residual developer on the photoreceptor is cleaned by a cleaning device.

[Problems to be Solved by the Invention] However, when cleaning residual developer on the photoreceptor, compared to cleaning black toner,
Many color toners have poor cleaning properties, and there is a problem in that these color toners tend to cause filming on the photoreceptor. The cause is still unknown, but it is probably due to the dyes and pigments that are the toner components. In addition, resins with low melt viscosity are often used for color toners for reasons such as improving color development and requiring translucency when transferred to sheets for overhead projectors. Therefore, cleaning performance tends to deteriorate further.

As a means to solve this problem, a method is proposed in which a small amount of a non-adhesive polymer additive having an average particle size smaller than that of each developer toner is mixed into the toner, thereby increasing cleaning efficiency (Japanese Patent Publication No. No. 1130), a method in which an abrasive is mixed into each developer and the abrasive is used to remove deposits on the photoreceptor during cleaning (Japanese Patent Laid-Open No. 57-204
576), a method in which the photoreceptor is a photoreceptor having a thermoplastic linear structure resin surface, a polishing device is provided separately from the cleaning device, and the polishing device removes deposits on the photoreceptor surface together with the resin ( Japanese Patent Publication No. 55-898
However, in a color image forming apparatus, it is time-consuming to mix an appropriate amount of an appropriate polymer additive or abrasive for each developer into each developer. , and there is also the problem that it is expensive. Furthermore, if additives or abrasives are mixed with color toners, this will affect color development and translucency, which is not preferable for color images that require subtle color tones.

Furthermore, using a photoreceptor having a thermoplastic linear resin surface and providing a separate polishing device requires time and effort, and the overall structure becomes complicated, resulting in an increase in cost.

Ru.

Therefore, the present invention eliminates the need to mix special additives or abrasives into the color developer, and also eliminates the need to separately provide a special device such as a polishing device, while effectively achieving filming with color toner. An object of the present invention is to provide a color image forming apparatus that can prevent the above problems and improve image reliability.

[Means to solve the problem]

As a result of research to achieve the above object, the inventor of the present invention found that, regarding filming with color toners other than black toner, developing with black toner on the photoreceptor and cleaning it with a cleaning device without transferring it. Ba,
It has been found that deposits such as the above-mentioned filming can be removed. Although the reason for the good cleaning caused by the black developer is not necessarily clear, it is thought that the carbon contained in a large amount in the black developer contributes to the cleaning.

Based on this knowledge, the present invention provides a means for causing a photoreceptor to be developed only by the black developing device outside of color image formation in a color image forming apparatus having a color developing device in addition to the black developing device, and The present invention provides a color image forming apparatus characterized in that it is equipped with a means for cleaning the photoreceptor after development without going through a transfer process.

Note that an abrasive may be mixed into the black developer if necessary. Since the black developer has a deep color, it has the advantage that even if an abrasive or the like is mixed therein, it has little effect on the image. Furthermore, since the black developer does not require transparency unlike color toners, it has the advantage that resins with high polishing effects can be used. Examples of the polishing agent include cerium oxide, silica, polysilsesquioxic acid, calcium carbonate, aluminum sulfate, barium sulfate, magnesium sulfate, aluminum oxide (alumina), strontium oxide, carbon random, and the like.

[For production]

According to the color image forming apparatus of the present invention, development is performed on the photoreceptor only by the black developing device at an appropriate time outside of color image formation, and the developed image is cleaned in the cleaning device without going through a transfer process. As a result, deposits such as filming formed by color toners other than the black developer are removed together.

When an abrasive is mixed into the black developer, the cleaning is performed more reliably.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

The color image forming apparatus described below is a full-color copying machine having cyan, magenta, and yellow color developing devices and a black developing device.

The illustrated copying machine is equipped with a photosensitive drum 8 in the center.
This drum is rotationally driven in the direction of arrow A in the figure by a drive means (not shown).

A charger 1 and a developing device 4 are installed around the photosensitive drum I.
．． 5.6 and 7, a transfer charger 10, a blade type cleaning device 140, and an eraser 21 are arranged in this order.

Developing device 4 contains magenta toner, 5 contains cyan toner, 6 contains yellow toner, and 7 contains black toner. Note that this black toner contains an abrasive.

The transfer charger 10 is housed in a transfer drum 9, and the drum 9 is provided with a known transfer material holding means (not shown).

A document platen glass (not shown) is provided above the photoconductor drum 8, and an optical system 3 is provided which scans the document image on the document platen glass and exposes the photoconductor 8 according to the image. .

A cassette (not shown) is provided on the side and below the transfer drum 9, and the transfer paper or transfer material for an overhead projector stored therein is sent out from the cassette by a paper feed roller (not shown), and transported by a conveyance roller (not shown). After being conveyed and having its timing adjusted by the timing roller device 22, it is held on the transfer drum 9 by a holding means (not shown) of the transfer drum 9.

Above the transfer drum 9, a conveyor belt 23 for receiving and transporting the transfer material from the drum, a fixing roller 11, 12 having an internal heater, a discharge roller (not shown), and a paper discharge tray are provided in this order.

The copying machine is controlled and operated by a control circuit 15 centered on a microcomputer.

The output port of this control circuit 15 is connected to the developing device drive circuit 15.
1 to the developing units 4, 5, 6 and 7, and to the charger l via the high voltage power supply 152;
It is connected to the transfer charger 10 via a high-voltage power supply 153 and to the eraser 21 via a lighting circuit 154, respectively. Note that the charger 1 is provided with a grid 2, which is kept at a constant potential. The output port of the control circuit 15 is also connected to the heater in the fixing roller 11 via a heater power supply 155, and to the heater in the fixing roller 12 via a heater power supply 1156, and a talker for counting the total number of copies. It is also connected to a clock counter 17.

In addition, a power switch 18 is connected to the input port of the control circuit I5.
A power supply 20 is connected through the printer 1, and a print switch 19, which is a start button, and a temperature sensor 16 of the fixing roller 11, 12 are connected, respectively.

Furthermore, the optical system 3 and other input/output loads are connected to the control circuit 15.

According to the copying machine, the power switch 18 is initially turned on, thereby turning on the heaters of the fixing rollers 11, 12 and starting warm-up.

During this warm-up, the photoreceptor drum 8 is driven to rotate and is charged by the charger l and the black developer 7 is activated, or the black developer 7 is activated and the gap between the photoreceptor drum 8 and the photoreceptor drum 8 is increased. A bias voltage is applied to form a black solid toner image on the photoreceptor drum 8. At this stage, transfer charger 1
The photoreceptor is cleaned with a cleaning blade 14 without operating the o, and the eraser 21 is turned on as necessary. After the photosensitive drum 8 is rubbed with the cleaning blade 14 for a predetermined period of time, the temperature of the fixing roller detected by the temperature detector 16 reaches a certain temperature T, and the warm-up is completed and the state is ready for printing. becomes. By solid black development and subsequent cleaning operation using a cleaning blade, deposits such as color toner filming on the photoreceptor drum are removed.

After the warm-up is completed, the print switch 19 is turned on and the color copying operation proceeds as follows.

First, a latent image to be developed with magenta is formed on the photoreceptor drum 8 by the optical system 3, and the latent image is transferred to the developing device 4.
The toner image obtained by the development is sent to the transfer charger 10 as it is, and the transfer material is supplied from a cassette (not shown) and reaches the transfer drum 9 via the timing roller device 22. ,
It is held here and rotates together with the drum in the direction B in the figure at the same speed as the photoreceptor 8. The magenta developed image on the photoreceptor drum 8 is transferred to the transfer charger lO portion of the drum 9.
Transferred to the upper transfer material. In this way, a latent image to be developed with cyan, a latent image to be developed with yellow, and a latent image to be developed with black toner are sequentially formed on the photoreceptor drum by the optical system, and these latent images are Developed by developing units 5, 6 and 7 in sequence.

Each time each latent image is developed with the color of the toner in the device by the corresponding developing device, the toner image thus obtained is sequentially superimposed on the transfer material on the transfer drum 9 at the transfer charger IO. transcribed.

After being released from the drum 9, the transfer material on which the toner images have been repeatedly transferred in different colors in this manner is conveyed by the conveyor belt 23 to the fixing rollers 11 and 12, where the toner on the transfer material is dissolved. These are then fixed onto the transfer material to form a predetermined color, and are then ejected to a paper ejection tray (not shown) by an ejection roller (not shown). Further, each time the toner image obtained by each developing device is transferred to the transfer material on the transfer drum 9, the residual toner on the photoreceptor drum l is scraped off by the cleaning blade 14 of the cleaning device 140, and the cleaner housing 13 and collected in a collection box (not shown). Furthermore, residual charges are erased by the eraser 21 and prepared for the next process.

The operation of the control circuit 15 that controls the series of operations of the copying machine will be explained based on the flowcharts shown in FIGS. 2 and 3.

FIG. 2 shows the main>V-chin control by the control circuit 15. According to this routine, initial settings are first performed in step Sl when the copying machine is turned on or when the copying machine returns after a trouble occurs, such as after clearing a jam. Next, in step S2, an internal timer is started. This internal timer determines the length of one routine of the main routine, and its value is set in advance in the initial setting at step 31.

Next, in step S3, it is determined whether the processed flag F+ indicating that the photosensitive drum cleaning process has been completed is "'0"°. This processed flag F1 is set at step 31.
It is set to “0°” by default. Step S
If the processed flag F is “0°°” in step S4, the photoconductor processing (cleaning processing) described later is performed in step S4.
Call the subroutine. Flag F is “1°”
If so, a copying process subroutine is called in step S5 to perform a normal copying operation. Since this copy processing subroutine is already known from conventional copying machines, its explanation will be omitted here. Then step S6
After performing other processing in step S7, the routine waits for the internal timer to end and ends the l routine. The time length of this l routine is used to count each timer appearing in various subroutines.

Next, the photoreceptor processing subroutine will be explained with reference to FIG.

In this routine, it is determined in step SIO whether the processing flag F2, which indicates that the photosensitive drum is being cleaned, is "0°".This processing flag is also set at the initial setting step SL described above. is set to “0°°”.

If the processing flag F2 is “0°” in step S10, the flag F2 is set to “0°” in step Sll.
11, and the timer TA is set in step S12. The timer TA is a sufficient time to form a solid black image on the photosensitive drum 8. Next, in step 313, the photosensitive drum 8 is rotated, and in step S14, solid black development is performed.

In step 310 described above, flag F2 is set to I11.
If this is the case, and if the black solid development is completed in step S14, it is determined in step S15 whether or not the counter of the timer TA has increased. If the timer TA has counted up, development is stopped in step S16, cleaning is started, and timer TB is set in step S517.

If the timer TA has not counted up in step 315, or if the timer TA has been set and then the step S
If 16.317 has been passed, the process advances to step 318.

Note that the above-mentioned timer TB has a sufficient time to clean the solid black developed image on the photoreceptor drum 8.

In step 318, it is determined whether or not the timer TB has counted up. If the timer TB has counted up, step 31
9, cleaning is stopped and the processed flag F is set to “1”.
At 0°, the processing flag F2 is set to 0° (steps 320, 321).

As described above, according to the above embodiment, after the power switch 18 is turned on and until the fixing roller 11. 8, any adhesion such as filming due to toner other than black is also removed.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various other ways.

In particular, regarding solid black development and subsequent cleaning processing, in addition to the above, conceivable methods include performing after continuous copying when the total number of copies exceeds a certain number, before or after each copy.

When cleaning is performed after continuous copying when the total number of copies exceeds a certain number, for example, if the number of copies exceeds 100, black solid development and cleaning may be performed after (continuous) printing.

When the cleaning process is performed every 100 prints in this way, the main routine controlled by the control circuit 15 is as shown in FIG.

Note that in the flowchart of FIG. 4, N indicates the number of prints.

In this case, the number of copies to date is read from the non-volatile memory in the initial setting of step S1, and when the copying operation in step S5 is completed (step 551).
, the number of copies is counted up in step 352, and when the number of copies reaches 100 (step 553), the counter is reset to O in step 354, and step S55
The processed flag F is reset to "0". In addition,
In this case, at the time of initial setting (31), the processed flag F is set to 0.1°.

Another possible method is to subject the photoreceptor to solid black development before or after each copy, and then perform a cleaning process. However, if the cleaning process is performed every time one sheet is copied, there will be a loss in the copying speed, so the black solid development and cleaning process may be performed after each continuous copy.

When cleaning is performed at the end of printing or before the start of printing, the main routine controlled by the control circuit 15 is as shown in FIG. In this case, the processed flag F1 is set to “
Set to 1”°.

Then, at the end of the copying operation in step S5 (step 5501), in step 5502, the processed flag F,
to “0°”. The processed flag F1, which has been reset to 0°, is then set to 1° in step S20 of the photoreceptor processing subroutine shown in FIG.

〔Effect of the invention〕

According to the present invention, there is no need to mix special additives or abrasives into the color developer, and the color development and translucency of the color toner can be maintained well, and the color developer can be used in a polishing device. It is possible to provide a color image forming device that does not require a separate special device, has a simple and inexpensive structure, and can effectively prevent filming due to color toner and improve image reliability. .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the main parts of a color copying machine according to an embodiment of the present invention, FIG. 2 is a flowchart showing a main routine of control by a control circuit in the color copying machine according to the first embodiment, and FIG. The flowchart of the photoreceptor cleaning processing subroutine, and FIGS. 4 and 5 are flowcharts showing other execution-side force operations. 4... Magenta developer, 5... Cyan developer, 6... Yellow developer, 7... Black developer, 8... Photosensitive drum, 140... Cleaning device, 15... - Control circuit, 16... Temperature detector, 17... Talk counter. Applicant for color copying machine: Minolta Camera Co., Ltd.

Claims (2)

[Claims] (1) In a color image forming apparatus having a color developing device in addition to a black developing device, a means for causing the photoreceptor to be developed only by the black developing device outside of color image formation, and a means for developing the photoreceptor only by the black developing device, and transferring after development by the black developing device only. A color image forming apparatus characterized by comprising a means for cleaning the photoreceptor without going through a process. (2) The color image forming apparatus according to claim 1, wherein the black developing device contains a black developer mixed with an abrasive.